Ivan’s Sierra II’s are “special” . They only made two, so far as I can tell, since they turned out to be lead pigs. The hulls are titanium which sounds neat but it has a fatal defect in a constant seawater atmosphere. The stuff “pinholes “ right straight thru. Putin might be trying to put a few miles on one before he has to either park it or bottom-fish for it.
Could that be because of the boats itself or because of the untrained/inexperienced crews that are manning them. Russians patrol their boats so infrequently that the crews can't be anything but rookies every time they sail.